Elucidation of spleen elasticity and viscosity in a carbon tetrachloride rat model of liver cirrhosis using a new ultrasound elastography.

Purpose: Measurement of spleen stiffness (SS) using ultrasound (US) elastography is useful for predicting portal hypertension. However, the mechanism leading to increased SS remains unclear. We jointly developed a new US elastography system (Aplio i-series, Canon Medical Systems) that can easily measure organ viscosity (dispersion slope: DS). We analyzed the cause of increased SS by calculating the shear wave speed (SWs, which reflects fibrosis) and DS of the spleen in carbon tetrachloride (CCL₄) rat liver cirrhosis models. Methods: A total of 13 Sprague–Dawley rats were randomly divided into four groups (C group: 3 rats as control, 2D group: 3 rats injected with CCL₄ twice in 1 week, 4D group: 4 rats injected 4 times in 1 week, 6W group: 3 rats injected twice a week for 6 weeks). The SWs and the DS of each group were calculated, and histopathological analysis was performed. Results: The spleen SWs of the 6W group was significantly higher than that of the C group (p = 0.044). The spleen DS did not change after CCL₄. The liver SWs of the 4D and 6W groups was significantly higher than that of the C group (p = 0.012 and 0.007, respectively) with fibrosis change on histopathology, and the DS of the 4D group was significantly higher than that of the C group (p = 0.033). Splenic fibrosis was confirmed in the 6W group, but inflammation and necrosis were not seen. Conclusion: SS increased due to fibrosis and can be predicted based on SWs and DS values. [ABSTRACT FROM AUTHOR]